Method of making insulating covers for bus bars



Nov. 21, 1950 G. J. MULLER 2,530,835

METHOD OF MAKING INSULATING COVERS FOR BUS BARS Original Filed Oct. 2,1945 INVENTOR. GEORGE J MULLER @MJL kM ATTORNEYS Patented Nov. 21, 1950METHOD OF MAKING INSULATING COVERS FOR BUS BARS George J. Muller,Philadelphia, Pa., assignor to Taylor Fibre 00., Norristown, Pa., acorporation of Delaware Original application October 2, 1945, Serial No.619,782. Divided and this application July 29, 1947, Serial No. 764,361

3 Claims.

This invention relates to an improvement in the method of makinginsulating covers for bus bars having metalized inner surfaces forcontact with conductors or bars such as shown in my application, SerialNo. 619,782, filed October 2, 1945, now Patent No. 2,439,859, of whichthis application is a division.

One of the objects of my invention is to provide a bus bar covering foreliminating the corona effect produced between the bus bar and itscovering, due to the minute air gap between the covering and the busbar, which corona produces carbon tracks on the surface of theinsulating cover and in time causes insulation failure.

Another object of my invention is to provide a bus bar cover haVing alining of copper or any other conducting metal, which can be groundedthrough a proper resistor to avoid the formation of a corona.

Another object of my invention is to provide a conducting lining whichwill be in contact with multitudinous places over the face of the busbar and at the same time be perfectly anchored throughout its entirearea to the covering.

Another object of my invention is the provision of a method by whichsuch covers can be made at a low cost and of the proper shape to beslipped on a bus bar, or a bar for conducting a high voltage current.

Having now described, in a general Way, the nature and purpose of thisinvention, I will proceed for illustrative purposes, to a description ofa preferred embodiment/thereof, with reference to the accompanyingdrawings, in which:

Figure 1 is a perspective view of a conductor bar having an insulatingcovering, in accordance with my invention;

Figure 2 is a perspective view of a portion of a mandrel, showing themethod of winding a covering thereon; and

Figure 3 is an end view of a completed cover.

In Figure l, the covering is designated by the reference character [0,on a conductor bar l2,

and M designates the metal lining, embedded in L the cover andcontacting with the conductor bar In the form shown the conductinglining is formed of copper screening, and the covering is formed ashereinafter described.

The reference character I6 designates a screw threaded through thelining and into contact with the metal lining, and connected to thescrew between nuts I8, I8, is a grounded wire having a resistor of theproper capacity therein to prevent the formation of a corona between theconductor and the covering.

The metal lining is preferably formed of copper screening, although anyother metal conducting screening, pierced, 0r perforated sheet may beused for the lining.

The covering is formed by supporting a mandrel l2 the shape of theconducting bar I2 for winding strip material, then winding a turn or twoof dielectric material It thereon, and then wrapping in the metal sheetM to produce an overlapping layer of the metal lining and thencontinuing the winding of dielectric material 10, until the requiredthickness of insulating wall is built up. J

After the covering on the bar or mandrel has been built up, the mandrelis removed from the winding supports, and is then placed in a propermold for compressing the dielectric material and after curing the coveris removed from the mandrel.

As the metal of the liner is harder or more dense than the dielectricmaterial, portions thereof will cut through the dielectric material andwill be exposed on the inner surface and will be in direct contact withthe face of a bar over which it is slipped.

The cover may be made in different lengths and may be sawed into variouslengths to cover the portions of bars to be insulated, and may then bedrilled and tapped for a grounding screw or the lining may be groundedin any desired manner.

Any type of dielectric material which requires molding after wrappingmay be used, but I preferably use a paper or fabric impregnated with asynthetic resin having insulating capacity, as, for example, a phenolformaldehyde type resin, and which may be applied by wrapping and thenformed in a mold under heat and pressure.

What I claim and desire to protect by Letters Patent is:

1. The method of producing covers for conductor bars having a metalizedlining for intimate contact with the surface thereof, comprisingproviding a mandrel whose cross-sectional contour and area is the sameas the contour and cross-sectional area of the bars to be covered, thenwinding a turn of foraminous sheet conducting metal on the mandrel toform the lining, then winding a plurality of turns of sheet insulatingmaterial on the foraminous sheet conducting metal to form a cover of thedesired wall thickness and density, then pressing the covering about themandrel while in a non-expansible space with sufficient pressure topress the foraminous sheet metal into intimate contact with the mandrelto form the metalized lining and to force insulating material into theforamina in the sheet conducting metal to anchor the metalized lining inthe insulating material, and then removing the cover from the mandrel.

2. The method of producing covers for conductor bars having a metalizedlining for intimate contact with the surface thereof, comprisingproviding a mandrel whose cross-sectional contour and area is the sameas the contour and cross-sectional area of the bars to be covered, thenwinding a turn of copper screening on the mandrel to form the lining,then winding a plurality of turns of sheet insulating material on thecopper screening to form a cover of the desired wall thickness anddensity, then pressing the covering about the mandrel while in anon-expansible space With sufficient pressure to press the screeninginto intimate contact with the mandrel to form the metalized lining andto force insulating material into the foramina in copper screening toanchor the metalized lining in the insulating material and then removingthe covers from the mandrel.

3. The method of producing covers for conductor bars having a metalizedlining for intimate contact with the surface thereof, comprisingproviding a mandrel whose cross-sectional contour and area is the sameas the contour and cross-sectional area of the bars to be covered, thenwinding a turn of sheet insulating material, then winding a turn ofcopper screening on the mandrel to form the lining, then winding aplurality of turns of sheet insulating material on the copper screeningto form a cover of the desired wall thickness and density, then pressingthe covering about the mandrel while in a non-expansible space withsuincient pressure to press portions of the screening through the sheetinsulating material on the mandrel and into intimate contact with themandrel and to press other portions of the screening into the insulatingmaterial to anchor the metalized lining in the insuluating material, andthen removing the cover from the mandrel.

GEORGE J. MULLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,052,106 Voorhees Feb. 4, 19182,069,891 Maclachlan Feb. 9, 1937 2,183,811 Homan Dec. 19, 19392,278,424 Campbell Apr. 7, 1942 2,298,748 Brown Oct. 13, 1942 2,303,283Kirkwood et a1. Nov. 24, 1942 2,309,903 Hume Feb, 2, 1943 2,312,227 YantFeb. 23, 1943 2,431,085 Shelmerdine et a1. Nov. 18, 1947 2,439,859Muller Apr. 20, 1948 2,470,599 Billmeyer May 17, 1949

